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I'm trying to joint some sound boards. I'm using a jointing plane on a shooting board. I'm getting very thin nice shavings from the entire length of the boards but when I hold them up to the light there is a gap in the middle. Why is this? How can I be taking a shaving from the whole edge but end up with 2 concave edges?

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We are all in the gutter but some of us are looking at guitars.

You are probably pushing on the front of the plane too hard.

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http://www.CostaGuitars.com
PMoMC

Various possibilities.

1. If your shooting board has an inclined base, then , if the cutting edge of your plane iron is not dead straight, it can produce a concave edge. Most times, plane irons should be sharpened with a very slight curve, but not when jointing a soundboard.

2. The sole of your plane may not be dead straight ...if it is slightly convex, then you will experience the symptoms you describe.

3. The iron may not be set fine enough (although you do say you are taking thin shavings)

IME, Stanley and Record planes are a total PITA, and if you are using one, then the best solution would be to upgrade to a Clifton or a Lie Nielsen.

That would result in two convex edges.

OP has two concave edges.

If your plane and blade check out OK, check the condition of the plates.
We tend to not worry about any slight bow on the plates when both jointing and joining, as the slighest pressure will flatten the plates.
But if the plates are not flat, it cause cause frustration when candling.

This can happen with a bookmatched joint- you've got the halves held down on the shooting board and jointing both edges at once. When you take the plates off the board for candling (inspecting with a light source), the plates are unfolded and the ever-so-slight bow is reversed from one plate to the other. This makes it more difficult to accurately determine the true condition of the joint.
If this is the case, the best method of candling is to lay the halves on a glass table with light shining underneath, allowing you to use hand pressure to flatten the halves as you push them together.
Just something to check before you start going nuts.

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Always have plenty of sandpaper; it's rough out there!

Todd:
I don't wish to be a nitt-picker but I think that you threw in an extra zero there. Maybe it is the one that should appear before the decimal point.

Bob

Everybody knows that Zero means nothing!

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I said that once in a math class. BIG mistake!

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Phil

http://www.oleninstruments.com

"Those who tilt at windmills are only considered insane by those who can't see the dragon."

The blade must be hair shaving sharp and the cut minimal. You don't want a solid shaving, but the thinest possible thing which can crumble by itself to something fluffy resembling dandelion chutes. With a good fore plane it takes me just a few passes to get a perfect joint and I don't use a shooting board, I simply grab a neck blank from the pile and hold the piece on it with the left hand.

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Build log

Thanks very much for all your imput. I thought my shavings were thin... but not thin enough! Your advice helps me a lot.
Todd, ever thought of writting a book?

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We are all in the gutter but some of us are looking at guitars.

I almost always have to adjust pressure to get the right cut. When candling the joint I make a mental note of where material needs to be left alone and where it needs to come off and apply pressure accordingly as I take the next cut, candle and do it again till it's right. I don't know if this is an example of poor technique that I simply got used to or if that's the norm for some of us. I usually get it pretty darn close. Sometimes I will see a bit of light escape at the ends but that's ok since it's going to be cut off anyway.

I usually finish the edges off by using a steel tube (it is precision ground for flatness off course). One side has 120 grit sanpaper and the other 240. The end result is a very tight fit between the two plates.

I think that's normal, especially if the grain changes direction along the length of the joint. It's nearly always concave or convex (rather than wavy) and I adjust the pressure accordingly.
Extremely sharp blade, well set up Plane (mine is a Record and a Stanley!) and a bit of practice.

Hi everyone,

Been away for a while working on wel work... ugh.. life. Anyway - with a mandolin about 85% I am starting a new classical guitar -

It is going to be a three piece back - the middle piece will be a wedge shape - any tips on jointing a back like this ? My first was a 3 piece back but it was not a wedge.
I have very little wood to waste - so I want to make sure I get everything perfect -

do you joint the two outer pieces first ? or joint one outer with the middle and then the other outer with the middle after gluing ? I can't imagine shooting/jointing all three at the same time.


thx !
John

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It's this new idea from recent decades that everyone gets a participation award. - MUX

I would joint each pair of mating surfaces, book matched on a flat shooting board; join all three pieces at the same time with end stops to prevent slipping along the center wedge.

Joe

*&%#@!@**** I jointed myself into a wider purfling .... ugh I was trying to avoid that - and I still don;t have a good joint. Chasing the joint - it is Bolivian rose and English walnut... I have more English, but I do not have more bolivian

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It's this new idea from recent decades that everyone gets a participation award. - MUX

Thanks Todd, I really appreciate it. Friday is my best day, not sure if you'll be around.
My plane is pretty good. I stopped trying for the night but will pick it up again tomorrow or Friday.
I'll let you know how it goes. I have done this many times, just this one is getting to me.

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It's this new idea from recent decades that everyone gets a participation award. - MUX

While we're on the subject, do most of you thickness your plates before or after jointing?

Rough them before and bring in to final thickness after joining.

+1 for this method

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Brad

Anybody have any luck using this for joining??
http://www.woodcraft.com/category/20003 ... ystem.aspx

Seems like it should work, but you'd want three or four of them and wax paper to prevent gluing the plates to the wooden bar. Looks like a mechanical version of roping: LMI's Plate Joining Jig

It looks like the small black block that presses on the side of the wood to be clamped is about 1/2" high. That might prevent anything thinner than 1/2" from working correctly in the clamp. Might want to call them to make sure you can clamp thin wood.